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use crate::types::{ParseError, Result};
use std::convert::TryInto;
const MAGIC_HEADER: &[u8] = &[0x49, 0x42, 0x53, 0x50];
const HEADER_LEN: usize = 4 + 4 + (17 * 4 * 2);
/// The header found at the start of a (Q3) bsp file
#[derive(Clone, Copy, Debug)]
pub struct Header {
pub version: u32,
pub dir_entries: [DirEntry; 17],
}
/// A directory entry, pointing to a lump in the file
#[derive(Clone, Copy, Debug)]
pub struct DirEntry {
/// Offset from beginning of file to start of lump
pub offset: u32,
/// Length of lump, multiple of 4.
pub length: u32,
}
impl Header {
/// Deserialise from buffer.
/// # Format
/// string[4] magic Magic number. Always "IBSP".
/// int version Version number. 0x2e for the BSP files distributed with Quake 3.
/// direntry[17] direntries Lump directory, seventeen entries.
pub fn from(v: &[u8]) -> Result<Header> {
if v.len() < HEADER_LEN {
return Err(ParseError::Invalid);
}
let magic = &v[0..4];
if magic != MAGIC_HEADER {
return Err(ParseError::Invalid);
}
let version: &[u8; 4] = v[4..8].try_into().unwrap();
let entries: &[u8] = &v[8..144];
let mut dir_entries: [DirEntry; 17] = [DirEntry {
offset: 0,
length: 0,
}; 17];
for n in 0..17 {
let base = &entries[(n * 8)..(n * 8) + 8];
dir_entries[n] = DirEntry {
offset: u32::from_le_bytes(base[0..4].try_into().unwrap()),
length: u32::from_le_bytes(base[4..8].try_into().unwrap()),
}
}
Ok(Header {
version: u32::from_le_bytes(*version),
dir_entries,
})
}
/// Get the lump at given index from the buffer, with offset & length based on this directory.
pub fn get_lump<'l>(&self, buf: &'l [u8], index: usize) -> &'l [u8] {
let entry = self.dir_entries[index];
&buf[entry.offset as usize..entry.offset as usize + entry.length as usize]
}
}
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